Fix wrong container name in README command.

README.md

@@ -4,7 +4,7 @@ This micro service enables you to upload pdf slides (e.g. lecture slides) and qu
 # Setup
 Pull the image. Replace the version number. If unknown look up the latest version here: https://hub.docker.com/r/fwelter/elastic-search-middleware
 
-`docker pull fwelter/elastic-search-middleware:<VERSION_NUMBER>`
+`docker pull fwelter/wilps_slide_index:<VERSION_NUMBER>`
 
 Run the image. Adjust the ports according to your setup. Most likly the containers needs to be put behind an 
 nginx or another webserver to ensure SSL encryption (see below for instructions).